Animals think (we think)

It is an easy test, and one that any parent can administer. Cut a banana in two and ask a hungry five-year-old to eat one piece. The child snatches the biggest one. But cut the banana in half, and the decision comes more slowly.

This doubt is an example of one of the most sophisticated mental talents humans possess. It is called cognitive self-awareness - the ability to wonder whether one is making the "right" judgement.

Humans do it effortlessly, but there is new evidence that some animals can do it too. In three simple but unusual experiments, researchers showed that rhesus monkeys and a bottlenose dolphin chose "I'm not sure" with virtually the same frequency as humans when offered difficult choices.

"They know when they don't know," said the lead researcher, John David Smith, a psychologist at the State University of New York. "You up the stakes and give them a behavioural way to opt out, and they take it. It's lovely to watch."

The Smith team's research offers fresh evidence in an enduring controversy among psychologists over if and how animals "know" things or think.

Some researchers, who accept that animals can move beyond simple instincts and predispositions to consciousness, praised the study.

But others dismissed it as one more unsuccessful effort to bestow significance on actions that result simply from environment and training.

The study conclusions are presented in the journal Behavioural and Brain Sciences.